Currently, high-performance permanent magnet materials occupy an important position in the national economy and high-tech development. With the development of emerging high-tech industries such as wind power generation, hybrid and pure electric vehicles, the demand for high-performance permanent magnet materials is increasing, and the research and development on such materials have shown an increasingly important strategic position.
Rare earth permanent magnet material is a type of high-performance permanent magnet materials formed by rare earth RE (Sm, Nd, Pr, etc.) and transition metal M (Fe, Co) and the like. In the periodic table of elements, rare earth element is a general term for 15 lanthanides. It should be pointed out that the Group IIIB elements—scandium and yttrium are often included as rare earth elements. The first generation of rare earth permanent magnet materials represented by SmCo5 as developed in the 1960s and the second generation of rare earth permanent magnet materials represented by Sm2Co17 as developed in the 1970s both have good permanent magnet properties. In 1983, Sakawa Masahito et al conducted extensive experiments on RE-Fe—X ternary alloy, and found that Nd—Fe—B magnet, which belongs to the third generation of rare earth permanent magnet materials, has a high maximum energy product. Nd—Fe—B magnet has a higher maximum energy product and a lower price, but has a lower Curie temperature and a poorer high temperature property as compared to Sm—Co permanent magnet.
In the early 90s of last century, people put forward the use of nano-technology to constitute nano-scale soft and hard magnetic phases into “an exchange coupled permanent magnet”, which opened a new idea for “next generation” of super strong permanent magnet materials. The theoretical energy product of this type of permanent magnet material reaches as high as 100 MGOe, far exceeding the highest energy product of the current “permanent magnet king” Nd2Fe14B, which is 64 MGOe. In addition, this type of permanent magnet material contains a large amount of cheap soft magnetic phase (such as Fe or FeCo etc.), and has a low rare earth content, and thus has a low cost and a good corrosion resistance.
One of the key indexes to measure the property of permanent magnet materials is the maximum energy product. Over the past 20 years, various types of permanent magnet materials have been prepared using various techniques such as mechanical alloying, rapid quenching, hot press deformation (e.g., die-upset) and the like.
Chinese patent CN1985338A discloses a bulk anisotropic nanocomposite rare earth permanent magnet. In this patent, a permanent magnet material is prepared by die-upset technique. As the patent uses rare earth-rich permanent magnet powder as a raw material, the permanent magnet material has a high content of rare earth elements and a relatively high cost.
Chinese patent CN1735947A discloses a composite rare earth permanent magnet material. In this patent, a rare earth alloy powder is prepared by melt spinning process, and then subjected to rapid hot press, to result in a SmCo9.5 permanent magnet material, which has a maximum energy product of 11.1 MGOe.
U.S. Pat. No. 2012/0153212 discloses a nanocomposite permanent magnet material. In this patent, a permanent magnet material is prepared by die-upset technique. The permanent magnet material is made from SmCo5+20 wt % Fe65Co35, and has a maximum energy product of 19.2 MGOe.
The prior art still needs permanent magnet materials with lower cost and better property, especially permanent magnet materials with a lower rare earth content and a higher maximum energy product.